Rockets were fired at northern Israel from Lebanon on Friday and Israel's army responded with artillery fire, Lebanese and Israeli military authorities said.
Southern Lebanon is a stronghold of Hezbollah, a Shi'ite Muslim group that battled Israel seven years ago and is engaged in Syria's civil war in support of President Bashar al-Assad, but there are also Palestinian groups in the same area. In the past, militants linked to al Qaeda have claimed such attacks.
The rockets were fired from the Marjayoun - Hasbaya area towards "occupied Palestinian territories", a statement from Lebanon's army said, referring to Israel. The projectiles were launched in the hours before dawn.
Lebanese security forces arrested a man suspected of firing the rockets, the national news agency said later in the day. He was Lebanese and a member of "fundamentalist groups", the report said, without naming the groups.
It said he had admitted he had been accompanied by two Palestinians who were also members of these groups, and security forces were still searching for the pair.
The army said it had discovered two missile platforms with more rockets ready for launch after searching the area, and had dismantled them.
An Israeli military spokeswoman said a lone rocket launched from either Lebanon or Syria landed in Israel's far north, ending up in an open area near a farming community close to the border with Lebanon. The army responded with artillery fire, she said.
There were five rockets fired in total from southern Lebanon, Lebanese security sources said. Two entered Israel, one fell into Lebanese territory and two more were intercepted.
An Israeli military spokeswoman confirmed that Israel responded with artillery fire. Israel shot back around 25 shells, the Lebanese army said, and there were no reports of casualties.
Israeli chief military spokesman Brigadier-General Motti Almoz said a rocket fell near Kibbutz Kfar Yuval and that the military was checking for more details on the source of the firing. There were no casualties or damage.
Palestinian militants in the Gaza Strip have launched hundreds of rockets into Israel since the start of an Israeli offensive four days ago, but Kfar Yuval is almost certainly out of range of those rockets.
At least 82 Palestinians, most of them civilians, have been killed in the offensive, which Israel says it launched to end persistent rocket attacks on civilians. Some rockets have reached Tel Aviv, Jerusalem and other cities.
In December, rockets launched from Lebanon struck northern Israel, provoking a response across a border that had been largely quiet since a war in 2006. In August, Brigades of Abdullah Azzam, an organisation linked to al Qaeda, claimed a rocket barrage from Lebanon.